OneOf property is failing during OAS Schema Validation about json-schema-spec HOT 4 CLOSED

components:
  schemas:
    BillableItemsPost:
      title: Billable Items Post Request
      description: Object defines JSON schema of SAP OTC Billable Items post request
      type: object
      discriminator:
        propertyName: product
        mapping:
          Generic: '#/components/schemas/BillableItemsPost'
      properties:
        billableHeader:
          description: Billable Item request header
          type: object
          additionalProperties: false
          properties:
            product:
              description: A discriminator property to identify the schema specifics
              type: string
              enum:
                - Generic
                - Airlcl
              example: Generic
              discriminator:
                propertyName: product
                mapping:
                  Generic: '#/components/schemas/BillableItemsPost'
            sourceSystem:
              description: Upstream System Name **Required for CW1**
              type: string
              minLength: 1
              maxLength: 6
              example: GCSS
            sourceTransactionType:
              description: >-
                Source Transaction Type(O- Booking Confirmed, L- Issue Verify
                Copy or Pre- Invoice Event, I- Invoice) **Required for CW1**
              type: string
              enum:
                - BOOKING_CONFIRMED
                - ISSUE_VERIFY_COPY
                - INVOICE
                - CREDIT
                - CREATE_REV
                - UPDATE_REV
                - CANCEL_REV
                - UPDATE_COST
                - CANCEL_COST
                - CANCEL_INVOICE
              example: INVOICE
            eventType:
              description: Event Type (Ad-hoc, Batch)
              type: string
              enum:
                - AD-HOC
                - BATCH
              example: BATCH
            messageCreationDatetime:
              description: >-
                Message Creation Timstamp, used for the message synchronizing to
                ensure message is picked in correct sequence **Required for
                CW1**
              type: string
              format: timestamp
              example: '20220811140203'
            timeZoneCode:
              description: >-
                Time Zone, Will be used if needed along-with TimeStamp
                **Required for CW1**
              type: string
              minLength: 1
              maxLength: 4
              example: GMT
            isBulkProcessing:

paths:
  /billable-items:
    post:
      summary: Create Billable Item
      description: Creates a new Billable Item in S/4 HANA
      tags:
        - Billable Item
      operationId: billable-item-post
      requestBody:
        content:
          application/json:
            schema:
              x-field-extra-annotation: '@com.fasterxml.jackson.annotation.JsonTypeInfo(
                use = com.fasterxml.jackson.annotation.JsonTypeInfo.Id.NAME,
                include = com.fasterxml.jackson.annotation.JsonTypeInfo.As.PROPERTY,
                property = "product")'
              x-class-extra-annotation: '@com.fasterxml.jackson.annotation.@JsonSubTypes({
                @JsonSubTypes.Type(value = BillableItemsPost.class, name = "Generic"),
                @JsonSubTypes.Type(value = BillableItemsPostAirlcl.class, name = "Airlcl")})'
              oneOf:
                - $ref: '#/components/schemas/BillableItemsPost'
                - $ref: '#/components/schemas/BillableItemsPostAirlcl'
              discriminator:
                propertyName: product
                mapping:
                  Generic: '#/components/schemas/BillableItemsPost'
                  Airlcl: '#/components/schemas/BillableItemsPostAirlcl'